Samarium(III) chloride, also known as samarium trichloride, is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

samarium Samarium is a chemical element with symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of samar ...

and

chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...

. It is a pale yellow salt that rapidly absorbs water to form a hexa

hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

, SmCl₃^.6H₂O. The compound has few practical applications but is used in laboratories for research on new compounds of samarium.

Structure

Like several related chlorides of the lanthanides and actinides, SmCl₃ crystallises in the UCl₃ motif. The Sm³⁺ centres are nine-coordinate, occupying trigonal prismatic sites with additional chloride ligands occupying the three square faces.

Preparation and reactions

SmCl₃ is prepared by the " ammonium chloride" route, which involves the initial synthesis of (NH₄)₂ mCl₅ This material can be prepared from the common starting materials at reaction temperatures of 230 °C from samarium oxide: ::10 NH₄Cl + Sm₂O₃ → 2 (NH₄)₂ mCl₅ + 6 NH₃ + 3 H₂O The pentachloride is then heated to 350-400 °C resulting in evolution of ammonium chloride and leaving a residue of the anhydrous trichloride: :: (NH₄)₂ mCl₅ → 2 NH₄Cl + SmCl₃ It can also be prepared from

metal and

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

. :2 Sm + 6 HCl → 2 SmCl₃ + 3 H₂ Aqueous solutions of samarium(III) chloride can be prepared by dissolving metallic

or samarium carbonate in

. Samarium(III) chloride is a moderately strong

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

, which ranks as "hard" according to the

HSAB concept HSAB concept is a jargon for "hard and soft (Lewis) acids and bases". HSAB is widely used in chemistry for explaining stability of compounds, reaction mechanisms and pathways. It assigns the terms 'hard' or 'soft', and 'acid' or 'base' to chemic ...

. Aqueous solutions of samarium chloride can be used to prepare samarium trifluoride: :SmCl₃ + 3 KF → SmF₃ + 3 KCl

Uses

Samarium(III) chloride is used for the preparation of

metal, which has a variety of uses, notably in

magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...

s. Anhydrous SmCl₃ is mixed with

sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...

calcium chloride Calcium chloride is an inorganic compound, a salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide. Ca ...

to give a low

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...

eutectic mixture.

Electrolysis In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...

of this molten salt solution gives the free

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

In laboratory

Samarium(III) chloride can also be used as a starting point for the preparation of other

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

s. The anhydrous

is used to prepare

organometallic Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

compounds of samarium, such as bis(pentamethylcyclopentadienyl)alkylsamarium(III) complexes.

References

{{Lanthanide halides Chlorides Samarium compounds Lanthanide halides